Two-Speed Shuffle

Replacing a Powerglide With A TPI TH350 Is a Smart Step

Every Chevy II Nova owner in the world knows the feeling of a "slip 'n' slide" two-speed transmission. That's because the only option with those early cars ('62-67) was a Powerglide, unless the original owner opted for a manual trans. The 'Glide offered a simple solution for these economy cars, but when it came to performance, they lacked street driveability under virtually every condition short of a big-block under wide-open throttle. Even with a rebuilt box in a small-block car, the tall gearing made the combination seem underpowered. The best solution for those wanting to conserve cash and stick with an automatic is the installation of the venerable Turbo-Hydramatic 350.

Our donor car offered the perfect opportunity to swap out the Powerglide with a custom-built 350 from TPI Performance. With close to 400 hp on tap, this little drop-top has plenty get up and go. Still, it was sluggish out of the hole and took a while to climb into the powerband with a Powerglide in the tunnel. Not only that, the rpm drop between First gear and High took the potent Mouse out of its torque range. A three-speed was just what this little Deuce needed.

TPI's Turbo 350 has much shorter gearing than the Powerglide. And adding the extra gear will give the car more momentum off the line that will carry all the way through the entire powerband. The best part about this swap is that it will enhance the overall driveability of the street machine. With less rpm drop between shifts the engine will maintain its torque and be more responsive when the throttle is mashed. Likewise, when cruising in High, since we didn't change the rearend gearing, the car will still be comfortable at highway speeds.

Installing the TPI TH350 was a relatively simple swap, since, dimensionally, it is the same as the Powerglide, which meant we didn't have to shorten the driveshaft or beat on the transmission tunnel. There were a couple of things we did have to convert, however, such as the shifter and the crossmember. Additionally, we had to run transmission cooler lines, since the TH350 routes the fluid to the radiator for cooling while the Powerglide relied on air to cool the transmission fluid. Another part of the swap was made easier by using a fabricated crossmember from Chevy 2 Only. A stock crossmember will work, but there is a small amount of modification that needs to be done to the leading edge. For the average do-it-yourselfer this isn't a big deal, but if you want a nice piece that simply allows the tranny to bolt in, go for the Chevy 2 Only part.

Since early Novas never came from the factory with a Turbo 350, there were no three-speed column shifters. In order to keep the factory column shifter, we used a special kit from Lokar, which consisted of a trick linkage arm for the transmission and the necessary rod and ends to connect it with the column mechanism.

Keeping with the performance portion of the swap, we installed a torque converter from TPI that had a stall speed of 2,800 rpm. This was the perfect combination to the firm shift that the trans provided. Now all the car needs is a Posi rearend.

In summary, with all the right pieces from TPI, Chevy 2 Only, and Lokar, our little Deuce retains that original look and takes on an added dimension of performance.

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Two-Speed Shuffle

The Powerglide transmission will have a kickdown bracket that is attached to a bellcrank then onto the carb linkage. We unbolted the attachment rod and the bracket from the top of the bellhousing. As for the linkage to the column, a quick pull of the pin, and the rod was removed. Since we had a complete Lokar shifter kit, it wasn't necessary to reuse the original linkage rod. If you don't choose to upgrade to a Lokar kit with custom spherical joints and a trick linkage arm, Chevy 2 Only has a stock upgrade kit to accommodate the three-speed swap to the stock column shifter.

Next, we removed the bolts that hold the torque converter to the flexplate. When the bolts are out, the converter will slide back into the transmission. Be sure to do this before trying to lower the tranny, as the converter may fall forward and out of the front pump, leaving you with a mess and the potential for a heavy part to fall on your foot.

With the linkage, speedo cable, and driveshaft removed from the trans we removed the bolts from the rear mount from inside the crossmember. Using a block of wood and a bottle jack, we lifted the trans off the crossmember.

Fortunately, we were able to reap the benefit of our Autolifters four-post lift to do this swap--much easier this way than on our backs in the driveway.

With the trans jacked up we removed the crossmember bolts. With the bolts from each side removed the crossmember slid out.

At this stage, using a long extension and the correct sockets, we removed the bellhousing bolts that held the trans to the back of the engine and slid the trans back. Notice the big circles in the Powerglide's bellhousing; this is where the air helped cool the converter and its tranny fluid.

With the trans removed from the car we installed the new SFI-approved flexplate from Mike's Transmissions. We recommend using a little Loctite on all the bolts and torquing them to the correct specs.

After removing the Powerglide (with a little extra muscle from our neighbors), the next task was the most difficult: installing the new TPI Performance TH350. We'd recommend doing it with a transmission jack, but a couple guys can install it with little trouble. We got the trans lined up on the dowels in the block and were lucky that a couple of the bolts started easily.

With the trans secure we installed the rubber trans mount and slid the new crossmember into place. This crossmember is from the Nova gurus at Chevy 2 Only and only fits in one way. With it in place we installed the fasteners that hold it in the frame. Note how the openings are slotted. This helped us to align everything easily.

Note how well the Chevy 2 Only crossmember fits in place. With it bolted in the subframe we installed the two bolts in the mount and reconnected the speedo.

The new Lokar kick-down cable bracket bolted to the manifold using the existing bolts. This end will attach to the carburetor; the rest will run down the firewall and fasten to the top of the trans.

At the trans the kick-down cable looks like this. The small end with the hole will attach to a hooked spring in the trans. There is a small boss where the bracket is bolted down.

Next, we lined up the converter and installed the bolts in the new TPI converter. This 10-inch converter has a 2,800-rpm stall and is really going to give this Nova some get up and go.

The new trans also needs new lines. Unlike the Powerglide, these trans lines will run fluid into the cooler in the radiator, thus keeping the trans from overheating.

We went with a Lokar dipstick for the trans. Made from aluminum and braided hose, it added a nice touch to the engine compartment, not to mention that it will make the task of checking the fluid easier.

These are the three main pieces to the Lokar mechanical shifter linkage upgrade. The knurled ring attaches to the trans and is secured by the polylock nut. The aluminum arm can be set at just about any angle needed.

The Lokar kit uses a universal rod that attaches to the stock column shifter bracket. The rod must be cut to length, then it is fit into this special sleeve which attaches to the aluminum trans arm via a spherical rod end. The shifter rod isn't threaded as it simply slides into the sleeve and is held in place with set screws.

There is ample adjustment to fit the linkage rod to the arm so that the angles are perfect.

Our last step was at the trans linkage. Using the supplied hardware, we fastened the rod to the bracket, which can slide back and forth in the aluminum arm.

This sharp-looking Nova convertible sports a nearly 400hp small-block and enough original restoration to proudly be called a sleeper. It has been meticulously built, yet the biggest limitation was the use of a Powerglide two-speed automatic trans. Using a stout TPI Performance TH350 and 2,400-stall-speed converter, plus a Lokar shifter and specialty hardware from Chevy 2 Only, our swap was a piece of cake.

With the car up and secure we started by removing the driveshaft. First, we removed the U-bolts, then pulled the shaft's yoke out of the trans. It is best to wrap the U-joint with masking tape so the caps can't fall off.

We remembered to remove the speedometer cable from the tailshaft. Make sure that it is out of the way when the trans is lowered out.

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